Cell Checkpoint Inhibitors Research Articles

Abstract IA-04: Pancreatic cancer cells assemble a CXCL12-keratin 19 coating to resist immunotherapy

Abstract How pancreatic ductal adenocarcinoma (PDA) cells stimulate CXCR4 to exclude T cells and resist T cell checkpoint inhibitors is not known. We find that CXCL12, the ligand forCXCR4 that is produced by the cancer-associated fibroblast, “coats” human PDA and colorectal cancer cells as covalent heterodimers with keratin 19 (KRT19). Modeling the formation of the heterodimer with three proteins shows that KRT19 binds CXCL12 and transglutaminase-2 (TGM2), and that TGM2 converts the reversible KRT19-CXCL12 complex into the covalent heterodimer. This model is validated by showing that cancer cells in mouse PDA tumors must express KRT19 and TGM2 to become coated with CXCL12, exclude T cells, and resist immunotherapy with anti-PD-1 antibody. Thus, PDA cells have a cell-autonomous means by which they capture CXCL12 to mediate immune suppression, which is potentially amenable to therapy. Citation Format: Douglas Fearon, Zhikai Wang. Pancreatic cancer cells assemble a CXCL12-keratin 19 coating to resist immunotherapy [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr IA-04.

Pre-Clinical Combination of AO-176, a Highly Differentiated Clinical Stage CD47 Antibody, with Either Azacitidine or Venetoclax Significantly Enhances DAMP Induction and Phagocytosis of Acute Myeloid Leukemia

While T cell checkpoint inhibitors are mainstays of cancer immunotherapy, therapies that direct innate immune responses against cancer are lacking. CD47, a "don't eat me" signal, is an innate immune cell checkpoint which binds SIRPα on macrophages and dendritic cells to limit phagocytosis and its upregulation on tumor cells leads to evasion of immune detection and clearance. Therapeutic antibodies have previously been developed to block CD47 and induce phagocytosis of tumor cells, thus validating the pathway. AO-176, a next generation humanized IgG2 anti-CD47 antibody, was developed to block the CD47/SIRPα interaction and induce tumor cell phagocytosis. Moreover, AO-176 directly kills tumor cells through a non-ADCC-dependent mechanism via induction of programmed cell death type III. In addition to these tumor eliminating properties, AO-176 has the potential for a strong safety profile as a result of its preferential binding to tumor versus normal cells, lack of RBC binding, and enhanced binding to tumor cells at acidic pH. CD47 has previously been shown to be upregulated on acute myeloid leukemia (AML) leukemic stem cells (LSC), enabling their expansion through evasion from phagocytic clearance. As a result, patients with increased CD47 on AML LSCs have worse overall survival. In this study, AO-176 efficacy was evaluated in AML cell lines as a single agent and in combination with azacitidine and venetoclax which are approved therapies for AML. Azacitidine is a cytosine analogue which acts to inhibit DNA methylation, and venetoclax is a potent Bcl-2 inhibitor. Previous studies have shown that azacitidine induces apoptosis of tumor cells and increases cell surface exposure of calreticulin, a DAMP (Damage Associate Molecular Pattern) which provides a strong pro-phagocytic signal. From these findings, it was hypothesized that azacitidine would enable increased tumor cell phagocytosis when combined with AO-176. The potential for a similar enhancement with a combination of AO-176 and venetoclax was also explored. The ability of AO-176, with or without azacitidine or venetoclax, to induce DAMPs on the surface of AML cells was assessed. Cell surface expression of DAMPs, calreticulin and PDIA3, were measured by flow cytometry. AO-176, azacitidine, and venetoclax as single agents potently increased both calreticulin and PDIA3 in a dose-dependent manner on AML cell lines such as HL60 This is the first time, to our knowledge, that venetoclax has been shown to induce DAMPs. To better understand the functional implications of these findings, in vitro phagocytosis assays were performed. Azacitidine and venetoclax significantly enhanced AO-176-mediated phagocytosis of AML cells compared to any of the agents alone. Moreover, when AO-176 was combined with azacitidine in direct tumor cell killing assays, enhanced activity was observed in a subset of AML cell lines. In conclusion, AO-176 combined with either azacitidine or venetoclax, resulted in significant enhancement of phagocytic AML cell clearance in vitro which also correlated with the ability of these agents to induce DAMPs. In vivo treatment with AO-176 in combination with these agents is in progress. AO-176 is being evaluated in phase 1 clinical trials for the treatment of patients with solid tumors (NCT03834948) and multiple myeloma (NCT04445701). Disclosures Donio: Arch Oncology: Current Employment, Current equity holder in private company. Wilson:Arch Oncology: Current Employment, Current equity holder in private company. Darwech:Arch Oncology: Current Employment, Current equity holder in private company. Andrejeva:Arch Oncology: Current Employment, Current equity holder in private company. Capoccia:Arch Oncology: Current Employment, Current equity holder in private company. Puro:Arch Oncology: Current Employment, Current equity holder in private company. Kashyap:Arch Oncology: Current Employment, Current equity holder in private company. Pereira:Arch Oncology: Current Employment, Current equity holder in private company.

Cite-Seq Profiling of T Cells in Multiple Myeloma Patients Undergoing BCMA Targeting CAR-T or Bites Immunotherapy

Adaptive T cell therapy using chimeric antigen receptor (CAR) T cells and bispecific T cell engagers (BiTEs) have demonstrated encouraging responses in heavily pre-treated multiple myeloma (MM) patients. However, the cellular and molecular predictors of clinical response are not fully understood as well as the mediators of acquired resistance remain elusive. Local immune suppression and T cell exhaustion are important mediators of responses therefore, it is plausible to speculate that a tolerant tumor microenvironment and the expansion of specific T cell populations may dictate clinical responses. In this study, we performed at the single cell level a broad immunophenotypic and transcriptomic characterization of the blood and bone marrow (BM) T cells of sensitive and resistant MM patients treated with adaptive T cell therapies. Using cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) we measured the expansion of variable T cell subsets, T cell specific activation and inhibitor markers and their functional states in order to identify cellular mediators of resistance to these adoptive immune therapies. Serial blood samples and BM aspirates (n=12) were collected from patients treated with anti-BCMA CAR-T or BCMA-CD3 BiTEs at variable time points, prior and post initiation of therapy and at relapse. Bone marrow mononuclear fractions were isolated through ficoll density gradients coupled with magnetic sorting of CD3pos T cells. Unbiased mRNA profiling coupled with feature barcoding technology for cell surface protein (TotalSeq-B) of BM CD3pos T cells was then performed by using the chromium single cell (10x Genomics). Paired-end sequencing was performed on Illumina platform. Cell Ranger and Seurat pipeline were used for sample de-multiplexing, barcode processing, single-cell 3′ gene counting, cell surface protein expression and data analysis. CAR-T cells were identified by the expression of the chimeric CAR-T cell transcript. The parallel measurement of transcripts and cell surface protein phenotypes of CD3pos T cells using a panel of 19 immune surface markers underlined the T cell repertoire diversity and identified different T cell subsets among the CD8pos and CD4pos T cells. Notably, the cell surface protein information overlaid on the transcript-generated UMA allowed accurate identification of all main immune clusters, in particular for the CD45RA and CD45RO positive cells. Comparison of CITE-Seq features revealed that the T cells composition of the blood and BM niches differed significantly between sensitive and resistant patients. As such an enrichment of CD4pos T cells with a higher CD4:CD8 ratio was noted in responding patients. Phenotypic (CD45RA, CD45RO, CD95, CCR7, CD62L, CD28, CD27) and transcriptional signatures (TCF7, LEF1, GATA3, EOMES, TBX21, PRDM1) also identified a higher proportion of memory like T cells (Tscm, Tcm) in responding patients. In contrast, T cells of resistant patients were enriched with terminally exhausted (Tex) and senescent cells with loss of CD28, high GMZHand GMZB, CD57pos, CD69pos and CD160pos as well as upregulation of TBX21. Expression of T cell checkpoint inhibitors such as LAG3, TIGIT and PD1 was high in these Tex cells as well as in some Tem. Of note, ex vivo T cell activation studies with TIGIT blockade demonstrated T cell activation in an autologous MM and T cell co-culture system with enhanced MM cells death. An expanded cluster of regulatory T cells (Treg) FOXP3pos,CD25pos was also observed in two resistant patients. Of note, no loss of BCMA transcript or surface expression was noted in MM cells at the time of acquired resistance. Single cell transcriptome of primary MM cells and chromatin accessibility (ATAC-seq) analyses of T cells of these patients are ongoing to investigate the transcriptional programs and epigenetic factors underlying the immune escape. Combined single cell features profiling of the transcriptome and surface protein expression of T cells from MM patients receiving BCMA targeted CAR-T or BiTEs therapies revealed potential mediators of resistance. In particular, T cells composition (low CD4:CD8 ratio and reduced population of Tscm, Tcm) along with an enrichment of terminally exhausted T cells are the main features observed in resistant patients. Delineating these mechanisms will guide future T cells engineering studies to enhance the efficacy and response durability of adoptive immunotherapy in MM. Disclosures McCulloch: Amgen: Honoraria; Sanofi: Honoraria; Celgene: Honoraria; Janssen: Honoraria. Duggan:Jannsen: Consultancy; Amgen: Consultancy; Novartis: Honoraria; Celgene: Consultancy; Astra Zeneca: Consultancy. Jimenez-Zepeda:Janssen, Celgene, Amgen, Takeda: Honoraria. Bahlis:AbbVie: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; GSK: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; BMS/Celgene and Janssen: Consultancy, Honoraria, Other: Travel, Accomodations, Research Funding; Karyopharm Therapeutics: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria. Neri:Celgene/BMS: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Amgen: Consultancy, Honoraria.

Advancement in Cancer Immunotherapy in Veterinary Medicine: A Review

Cancer is one of the leading cause of death in human beings throughout the world. Attempts to treat cancer are made but not effectively. Surgical removal, use of radiation therapy, chemotherapy and combination of these therapies have been tried to cure cancer but every therapy had its own side effects. Due to potential side effects, these therapies failed to develop as the permanent cure for cancer. Stem cell transplantation has also been attempted as an alternative but the recovery rate was very low. The most recent therapy, nowadays, to treat cancer is immunotherapy in which utilises the immunity of the patient to get modulated in such a way that cancerous cells get killed. So this review enlightens the eminent immunotherapies used for veterinary patients. T cell checkpoint inhibitors, engineered T cells, cancer vaccines, and anti-B and anti-T cell antibodies are amongst the important immunotherapies used in human as well as veterinary patient. Inhibition of T cell checkpoint molecules, such as PD-1 and CTLA-4, using monoclonal antibodies are the most advanced techniques developed in humans. These significant immunotherapies have achieved notable success against some of the advanced tumors in humans, including melanoma, renal cell carcinoma and non small cell lung cancer. However, a recent clinical trial with a caninized monoclonal antibody against canine PD-L1 showed response in canine melanoma.

Immuno-Oncotherapeutic Approaches in Advanced Hepatocellular Carcinoma.

Advanced hepatocellular carcinoma has limited treatment options, but there has been extensive growth recently with cabozantinib, regorafenib, lenvatinib, nivolumab, atezolizumab, and bevacizumab, which are some of the treatments that have received FDA approval just over the last three years. Because HCC tumor microenvironment is potentially immunogenic and typically characterized by inflammation, immunotherapy has been proposed as a potential novel therapeutic approach, which has prompted studies in advanced HCC patients investigating various immune-therapeutic strategies such as CAR-T cell therapy, checkpoint inhibitors, and onco-vaccines. The anti-PD-1 checkpoint inhibitors nivolumab and pembrolizumab have been FDA approved as a second line treatment in patients who progressed or are intolerant to Sorafenib. To build up on the success of PD-1 monotherapy, combinatorial regimens with PD-1/PD-L1 inhibitors plus VEGF targeted agents have shown positive results in various malignancies including HCC. The combination of atezolizumab plus bevacizumab is the new addition to the HCC treatment armamentarium following a pivotal study that demonstrated an improvement in OS over frontline sorafenib. Other novel immune-based approaches and oncolytic viruses are in the early phases of clinical evaluation. These innovative approaches enhance the intensity of cancer-directed immune responses and will potentially impact the outlook of this aggressive disease.

Immunotherapeutics to Treat HIV in the Central Nervous System.

The application of immunotherapies to HIV presents a new horizon of treatment options, but little is known about what impact they may have on the central nervous system (CNS). Here we review the most promising immunotherapeutic strategies that can be used to target HIV in the CNS and focus on identifying their potential benefits while exploring the challenges that remain in their application. We have identified five immunotherapeutic strategies that hold potential in managing CNS disease among HIV-infected patients. These include broadly neutralizing antibodies, multi-affinity antibodies, CAR-T cell therapy, checkpoint inhibitors, and therapeutic vaccines. Each class of immunotherapy presents unique mechanisms by which CNS viremia and latency may be addressed but are faced with several challenges. CAR-T cell therapy and multi-affinity antibodies seem to hold promise, but combination therapy is likely to be most effective. However, more human trials are needed before the clinical benefits of these therapies are realized.

Characterization of autologous T cells engineered to express NY-ESO-1 TCR with multiplexed CRISPR/Cas9 editing (NYCE T Cells)

Background & Aim NY-ESO-1 is a cancer testis antigen with ectopic expression on multiple myeloma (MM), melanoma and sarcoma but restricted expression on normal tissues, rendering it a good candidate target for cancer immunotherapy. We recently reported a phase 1 pilot trial of multiplex CRISPR/Cas9 genome-edited NY-ESO-1 TCR cells (NYCE T cells; NCT03399448) for patients (pts) with advanced MM, synovial sarcoma and myxoid/round cell liposarcoma (MRCL) demonstrated safety and feasibility as well as persistence of T cells. Here, we characterize the phenotype and function of the ex vivo manufactured NYCE T cells from the 3 pts that were infused in the trial. Methods, Results & Conclusion The 3 infusion products (2 MM – pt #35 and Pt #7, and 1 MRCL – pt #39) were used to compare expanded T cells with either CRISPR/Cas9 editing without TCR transduction or with Mock-editing and TCR transduction from the same pt. We examined the phenotypic markers of T cell differentiation and checkpoint inhibitors by multicolor flow cytometry and assessed in vitro anti-tumor efficacy via a luciferase-based killing assay. We found heterogeneity in the composition of T cell subsets from all 3 infusion products with various CD4 and CD8 ratios, ranging from 0.12-1.1. Transduction efficiencies (determined by Vbeta8.1+ staining) varied between 1-11% and different levels of knockout efficiency in TRAC, TRBC and PDCD1 genes were observed by digital PCR. Three NYCE T cell infusion products displayed a terminally differentiated T cell phenotype similar to CRISPR/Cas9 edited counterpart. In contrast to Mock-edited T cells from the same pt, NYCE T cells exhibited lower levels of differing combinations of exhaustion-associated markers (PD1, TIM3, LAG3, EOMES and CTLA4) in both CD4+ and CD8+ T cell compartments. All 3 infusion products elicited antigen-specific killing of NY-ESO-1 expressing target cells. We demonstrate that NYCE T cells are heterogeneous in composition. Furthermore, we showed that CRISPR/Cas9 editing does not affect T cell differentiation and anti-tumor efficacy, but does reduce levels of exhaustion-associated markers expressed by the final products. This work provides an in-depth characterization of the heterogeneous product composition and function of the first multiplex CRISPR/Cas9-edited T cells tested in humans.

Abstract A10: Fusobacteria upregulates PD-L1 in head and neck cancer cell lines: Potential mechanism for immune evasion

Abstract Objectives: Head and neck squamous cell carcinoma (HNSCC) is the 6th most common cancer worldwide with a poor prognosis of ~40% at 5 years for HPV-negative disease. Recently, immune checkpoint inhibitors (specifically, anti-PD-1 checkpoint inhibitors that block the PD-L1/PD-1 immunosuppressive axis) have been approved as a treatment for patients with recurrent/metastatic HNSCC. However, most patients (>80%) fail to respond to checkpoint inhibitors. PD-L1 expression on tumors plays an important role in immune evasion and can also influence response to checkpoint inhibitors. Tumor PD-L1 expression has been shown to correlate with checkpoint response. Factors that might affect PDL1 expression in HNSCC remain unclear. In this study, we explored the effect of periodontal bacteria, which has been associated with oral cancer, on PD-L1 expression in oral cancer cells. Materials and Methods: 303 HNSCC were compared to 37 adjacent control tissues in the TCGA mRNA expression database (RNASeq V2); the analysis was done based on tumor types. RT-PCR and flow cytometry were used to measure the base line expression of PD-L1 in seven head and neck cancer cell lines and human oral tissues. OQ01, an oral cancer cell line, was infected with four periodontal bacteria (Tanneralla forsynthia, Treponema denticola, Porphyromonas gingivalis, and Fusobacterium nucleatum). OQ01 and RPMI2650 cells were infected with two different strains of Fusobacteria (F. periodonticum, F. vincentii). The relative changes in expression of PLD1 was measured using RT-PCR in cell lysate after RNA isolation. PD-L1 protein level on the cell surface was measured using flow cytometry. Results: TCGA data analysis revealed that PDL1 was significantly (P< 0.0005) elevated in total cancer tissues compared to total controls. In the same data analysis, PDL1 expression was significantly (P< 0.05) elevated in oral cavity tumor compared to normal control. Expression of PD-L1 was variable among head and neck cancer patients and cell lines. Both F. nucleatum and P. gingivalis were able to enhance PD-L1 expression in OQ01 cells (10 and 15 fold, respectively). Two strains of Fusobacteria tested (F. periodonticum, F. vincentii) were also able to induce PD-L1 both at the mRNA (P< 0.005 and P< 0.05 respectively) and protein level in OQ01 and RPMI 2650 cells. Interestingly, the same strains of Fusobacteria enhanced MYC expression in OQ01 and RPMI 2650 cells. As a transcription factor MYC has been reported to regulate PDL1 transcription. These data along with our results suggest that Fusobacterial upregulation of PD-L1 expression might be through MYC enhanced expression. Conclusions: This study revealed that Fusobacteria enhance PD-L1 expression on HNSCC cancer cell lines, possibly through upregulation of MYC. This may have implications on cancer cell immune evasion and checkpoint inhibitor treatment response. Note: This abstract was not presented at the conference. Citation Format: Amani Harrandah, Rekha Rani Grag, Yuk Pheel Park, Sasanka S. Chukkapalli, Nikhita Yadlapalli, Edward K. L. Chan, Natalie Silver. Fusobacteria upregulates PD-L1 in head and neck cancer cell lines: Potential mechanism for immune evasion [abstract]. In: Proceedings of the AACR Special Conference on the Microbiome, Viruses, and Cancer; 2020 Feb 21-24; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2020;80(8 Suppl):Abstract nr A10.

T cell costimulation, checkpoint inhibitors and anti-tumor therapy

The hallmarks of the adaptive immune response are specificity and memory. The cellular response is mediated by T cells which express cell surface T cell receptors (TCRs) that recognize peptide antigens in complex with major histocompatibility complex (MHC) molecules on antigen presenting cells (APCs). However, binding of cognate TCRs with MHC-peptide complexes alone (signal 1) does not trigger optimal T cell activation. In addition to signal 1, the binding of positive and negative costimulatory receptors to their ligands modulates T cell activation. This complex signaling network prevents aberrant activation of T cells. CD28 is the main positive costimulatory receptor on naı¨ve T cells; upon activation, CTLA4 is induced but reduces T cell activation. Further studies led to the identification of additional negative costimulatory receptors known as checkpoints, e.g. PD1. This review chronicles the basic studies in T cell costimulation that led to the discovery of checkpoint inhibitors, i.e. antibodies to negative costimulatory receptors (e.g. CTLA4 and PD1) which reduce tumor growth. This discovery has been recognized with the award of the 2018 Nobel prize in Physiology/Medicine. This review highlights the structural and functional roles of costimulatory receptors, the mechanisms by which checkpoint inhibitors work, the challenges encountered and future prospects.

Therapeutic Targeting of the Macrophage Immune Checkpoint CD47 in Myeloid Malignancies.

In recent years, immunotherapies have been clinically investigated in AML and other myeloid malignancies. While most of these are focused on stimulating the adaptive immune system (including T cell checkpoint inhibitors), several key approaches targeting the innate immune system have been identified. Macrophages are a key cell type in the innate immune response with CD47 being identified as a dominant macrophage checkpoint. CD47 is a “do not eat me” signal, overexpressed in myeloid malignancies that leads to tumor evasion of phagocytosis by macrophages. Blockade of CD47 leads to engulfment of leukemic cells and therapeutic elimination. Pre-clinical data has demonstrated robust anti-cancer activity in multiple hematologic malignancies including AML and myelodysplastic syndrome (MDS). In addition, clinical studies have been underway with CD47 targeting agents in both AML and MDS as monotherapy and in combination. This review will describe the role of CD47 in myeloid malignancies and pre-clinical data supporting CD47 targeting. In addition, initial clinical data of CD47 targeting in AML/MDS will be reviewed, and including the first-in-class anti-CD47 antibody magrolimab.

Harnessing NK Cells for Cancer Treatment.

In the last years, natural killer (NK) cell-based immunotherapy has emerged as a promising therapeutic approach for solid tumors and hematological malignancies. NK cells are innate lymphocytes with an array of functional competences, including anti-cancer, anti-viral, and anti-graft-vs.-host disease potential. The intriguing idea of harnessing such potent innate immune system effectors for cancer treatment led to the development of clinical trials based on the adoptive therapy of NK cells or on the use of monoclonal antibodies targeting the main NK cell immune checkpoints. Indeed, checkpoint immunotherapy that targets inhibitory receptors of T cells, reversing their functional blocking, marked a breakthrough in anticancer therapy, opening new approaches for cancer immunotherapy and resulted in extensive research on immune checkpoints. However, the clinical efficacy of T cell-based immunotherapy presents a series of limitations, including the inability of T cells to recognize and kill HLA-Ineg tumor cells. For these reasons, new strategies for cancer immunotherapy are now focusing on NK cells. Blockade with NK cell checkpoint inhibitors that reverse their functional block may overcome the limitations of T cell-based immunotherapy, mainly against HLA-Ineg tumor targets. Here, we discuss recent anti-tumor approaches based on mAb-mediated blocking of immune checkpoints (either restricted to NK cells or shared with T cells), used either as a single agent or in combination with other compounds, that have demonstrated promising clinical responses in both solid tumors and hematological malignancies.

Increasing Responses to T-Cell Therapies in Solid Tumours by the Use of an Engineered Adenovirus Coding for TNFa and IL-2

Abstract Background During the last decade, a revived enthusiasm about T-cell related therapies emerged after promising clinical outcomes. Nevertheless, many patients (especially with solid tumours) still do not have adequate therapeutic options. The complexity of the tumour microenvironment is a likely factor acting in detriment of many of those therapies by multiple suppressive mechanisms. To tackle a complex mechanism, an oncolytic adenovirus 2 (Ad5/3-E2F-d24-hTNFa-IRES-hIL2, a.k.a. TILT-123) was engineered to enable T-cell therapies in those circumstances. Methods To study the efficacy of TILT-123 together with different T-cell related therapies (adoptive cell transfer, checkpoint inhibitors and CAR T cell therapy) different models were used including mouse, Syrian Hamster and patient derived in vivo models for different indications were tested. Results Antitumor efficacy analyses showed complete responses in all animals receiving a T-cell therapy or checkpoint inihibitor (aPD1 or aPDL-1) and the T-cell enabling virus. Further, other aspects such as safety, influence on different immune populations, abscopal effect, antitumor memory and ability to replace lympho-depleting chemotherapy and postconditioning with high-dose IL-2 treatment were studied. Conclusion The use of TILT-123 to enable T-cell therapies (including checkpoint-inhibiting antibodies) delivered encouraging preclinical results pointing to it as a valuable approach to increase the number of patients that benefit from T-cell therapies. Those results include not only cell based therapies but also checkpoint inhibitors, a kind of therapy that is making the difference in the field and becoming first-line treatment for an increasing number of indications. Because of the favourable preclinical studies, the first in human clinical trials with TILT-123 will start in the upcoming months. Legal entity responsible for the study The authors. Funding TILT Biotherapeutics. Disclosure V. Cervera-Carrascon: Full / Part-time employment: TILT Biotherapeutics. R. Havunen: Full / Part-time employment: TILT Biotherapeutics. J.M. Santos: Full / Part-time employment: TILT Biotherapeutics. A. Hemminki: Shareholder / Stockholder / Stock options, Full / Part-time employment, Officer / Board of Directors: TILT Biotherapeutics. All other authors have declared no conflicts of interest.

Portia: A Phase 1b Study Evaluating Safety and Efficacy of Tisagenlecleucel and Pembrolizumab in Patients with Relapsed/Refractory Diffuse Large B-Cell Lymphoma

Portia: A Phase 1b Study Evaluating Safety and Efficacy of Tisagenlecleucel and Pembrolizumab in Patients with Relapsed/Refractory Diffuse Large B-Cell Lymphoma

The Rise of NK Cell Checkpoints as Promising Therapeutic Targets in Cancer Immunotherapy.

Checkpoint immunotherapy that targets inhibitory receptors of T cells, thereby reversing the functional exhaustion of T cells, marks a breakthrough in anticancer therapy. The success of T cell-directed checkpoint inhibitors of CTLA-4 and PD-1/PD-L1 has opened a new approach for cancer immunotherapy and resulted in extensive research on immune checkpoints. However, it is only in recent years that research on NK cell exhaustion and potential checkpoints impacting NK cells has become popular. NK cells, as the major player in innate immunity, are critical for immune surveillance, particularly the control of metastasis and hematological cancers. The balance between activating and inhibitory signals fine tunes the activation and effector functions of NK cells, and transformed cells modulate NK cells by upregulating negative signaling that “exhausts” NK cells. Exhausted NK cells with excessive expression of inhibitory receptors (checkpoint molecules) are impaired in the recognition of tumor cells as well as antitumor cytotoxicity and cytokine secretion. Therefore, an understanding of the potential checkpoint molecules involved in NK cell exhaustion is particularly important in terms of NK cell-targeted cancer immunotherapy. In this review, we summarize recent advances in NK cell checkpoint inhibitors and their progress in clinical trials. Moreover, we highlight some of the latest findings in fundamental NK cell receptor biology and propose potential NK cell checkpoint molecules for future immunotherapeutic applications.

Abstract 4131: Overcoming aryl hydrocarbon receptor mediated tumor immunosuppression

Abstract Checkpoint inhibitors (CPIs) have become the cornerstone of immune-based oncology therapy; still many cancer patients do not benefit from these agents. Resistance to checkpoint inhibitors is due in part to the presence of immunosuppressive molecules which prevent immune activation despite T cell checkpoint inhibition. Aryl Hydrocarbon Receptor (AHR) is a transcription factor that mediates the immune response in multiple innate and adaptive immune cells subsequent to binding of a diverse set of endogenous and exogenous ligands. One such AHR agonist is kynurenine. Kynurenine, metabolized from tryptophan by indoleamine-pyrrole 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase 2 (TDO2), binds to AHR and leads to a net immunosuppressive tumor microenvironment. Given that kynurenine can be synthesized by both IDO1 and TDO2 and that AHR is activated by endogenous ligands other than kynurenine, AHR inhibition provides a novel approach to reverse immunosuppression in a broad range of tumor types. We demonstrated that AHR antagonism affects multiple immune cell types and can lead to pro-inflammatory phenotypes in human T cells and myeloid cells in vitro and in murine tumor models. AHR antagonism inhibits growth in the B16-IDO, CT26 and MC38 models and reverses the immunosuppressive microenvironment as indicated by changes in T cell and myeloid cell populations. Immune signature changes characterized via Nanostring in multiple tumor models treated with AHR antagonists were also assessed. Oral dosing of AHR antagonists led to tumor growth inhibition as a single agent and increased anti-tumor activity when combined with checkpoint inhibitors. In addition, beneficial anti-tumor activity occurred with AHR antagonists combined with chemotherapy or with radiation therapy in syngeneic mouse tumor models. Our data indicate that reversing AHR-mediated immune suppression in the tumor microenvironment drives anti-tumor activity alone and in combination with other therapeutic modalities. Overall, our data demonstrates that AHR is an attractive target for reversing immune suppression in tumors. Therefore, we are developing AHR antagonists and translational insights to treat patients most likely to benefit from this approach. Citation Format: Jeremy Tchaicha, Silvia Coma, Meghan Walsh, Jill Cavanaugh, Marta Sanchez-Martin, X. Michelle Zhang, Alfredo Castro, Jeff Ecsedy, Mark Manfredi, Karen McGovern. Overcoming aryl hydrocarbon receptor mediated tumor immunosuppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4131.

CAR-T with License to Kill Solid Tumors in Search of a Winning Strategy.

Artificial receptors designed for adoptive immune therapies need to absolve dual functions: antigen recognition and abilities to trigger the lytic machinery of reprogrammed effector T lymphocytes. In this way, CAR-T cells deliver their cytotoxic hit to cancer cells expressing targeted tumor antigens, bypassing the limitation of HLA-restricted antigen recognition. Expanding technologies have proposed a wide repertoire of soluble and cellular “immunological weapons” to kill tumor cells; they include monoclonal antibodies recognizing tumor associated antigens on tumor cells and immune cell checkpoint inhibition receptors expressed on tumor specific T cells. Moreover, a wide range of formidable chimeric antigen receptors diversely conceived to sustain quality, strength and duration of signals delivered by engineered T cells have been designed to specifically target tumor cells while minimize off-target toxicities. The latter immunological weapons have shown distinct efficacy and outstanding palmarès in curing leukemia, but limited and durable effects for solid tumors. General experience with checkpoint inhibitors and CAR-T cell immunotherapy has identified a series of variables, weaknesses and strengths, influencing the clinical outcome of the oncologic illness. These aspects will be shortly outlined with the intent of identifying the still “missing strategy” to combat epithelial cancers.

Disruption of CTLA-4 expression on peripheral blood CD8 + T cell enhances anti-tumor efficacy in bladder cancer.

Activation of programmed death-1 (PD-1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) on T cells leads to T cell exhaustion and ultimately facilitates tumor progression. Recent success of using immune cell checkpoint inhibitors offers a great promise to treat various cancers, including bladder cancer. However, the expression pattern and therapeutic value of PD-1 and CTLA-4 in peripheral blood T cells remain largely unexplored. In this study, we presume that disruption of the potential dysregulated checkpoint molecules in peripheral blood T cells may improve the anti-tumor efficacy of cytotoxic T cells in bladder cancer. We showed that both PD-1 and CTLA-4 expression were specifically elevated on CD8 + T cells but not CD4 + T cells in peripheral blood of patients with bladder cancer compared with that in healthy donors. Notably, CTLA-4 expression was significantly higher in muscle-invasive bladder cancer (MIBC) and correlated with tumor size. By blocking CTLA-4 with anti-CTLA-4 antibody and CRISPR-Cas9-mediated CTLA-4 disruption, we revealed that CTLA-4-disrupted CTLs had enhanced cellular immune response and superior cytotoxicity to the CD80/CD86-positive bladder cancer cells in vitro. Moreover, the CTLA-4-disrupted CTLs exhibited a pronounced anti-tumor effect in vivo as demonstrated by prophylactic assay and therapeutic assay in the subcutaneous xenograft model. Collectively, our findings confirm improved therapeutic efficacy of CTLA-4-disrupted CTLs and provides the potential strategy for targeting immune checkpoints to enhance the promising immunotherapy.

CD84: A Potential Novel Therapeutic Target in Multiple Myeloma

Introduction: Multiple Myeloma (MM) cell survival strictly depends on the interaction with multiple cell types in the bone marrow (BM), collectively referred to as the MM microenvironment (MM-ME). CD84 (SLAMF5) belongs to the signaling lymphocyte activation molecule family of immunoreceptors; previous data from our group have shown that CD84 mediates malignant B cells and their ME (Marom et al. 2017); however, its role within the MM-ME has not yet been investigated.Results: Using the MMRF CoMMpass IA9 dataset, we found that CD84 mRNA expression is low or absent in CD138+MM cells isolated from 660 newly diagnosed patients. In agreement with these data, flow analysis showed an absence of CD84 expression in all MM cell lines tested (n=9) and minimal surface expression (5.5-13%) in primary cells (n=3). However, a significantly higher expression of CD84 was detected on the surface of BM and peripheral blood (PB) monocytic fractions (CD14+) (76-97%) compared to that of matched CD14 negative fractions (2-9%) obtained from 16 different MM patients (p<0.001). Since it was recently reported that CD14+ monocytic myeloid derived suppressor cells (Mo-MDSCs) play a pivotal role in supporting MM growth by creating an immunosuppressive ME, we investigated CD84 expression in this population. Using primary PB (n=9) and BM (n=3) samples obtained from MM patients with active disease, we found that the Mo-MDSC population is significantly over-represented (0.34-2.88%) in MM patients compared to the PB from healthy donors (n=7) (0.04-0.45%) (p<0.05) and that CD84 is also significantly up-regulated in this population in MM patients (43-92%) compared to healthy donors (7-21%) (p<0.001).Next, to understand whether the expansion of Mo-MDSC and associated CD84 up-regulation is directly dependent on the MM cells, we investigated Mo-MDSC expansion and CD84 expression in two different MM mouse models. Specifically, 5TGM1 murine MM cells were IV injected into syngeneic immune-competent KaLwRijHsd mice (n=7), and human MM.1S cells were IV injected into immune-deficient NSG mice (n=10). Our data show that MM progression leads to significant Mo-MDSC expansion (p<0.0001) and a subsequent increase in CD84 levels (p<0.05) on this population in both mouse models.Since T cell checkpoint inhibitors PD-1/PD-L1 are tumor immune escape receptors that play a pivotal role in supporting an immunosuppressive MM-ME, we also investigated the expression of PD-L1 on the CD14+ fraction in MM patients. BM-CD14+ cells (n=3) were compared with matched CD14 negative cells. We found that the CD14+ fraction had a higher PD-L1 expression in the BM of MM patients compared to the CD14 negative fraction (60-96% versus 3-8%). Hence, we investigated whether CD84-mediated cell-cell contact may increase the level of PD-L1 expression on Mo-MDSCs and whether MM cells can regulate CD84 and PD-L1 expression on CD14+ cells. Co-culture assays were performed using several human MM cell lines (MM1S, U266 and KMS11) with PB CD14+ cells derived from healthy donors (n=3). Our data show a 1.9-fold increase from the basal level of CD84 (27±16% to 50±9.4%) and a 2.9-fold increase from the basal level of PD-L1 (18±8.5% to 52.3±5.7%).Our recently generated mouse anti-human CD84 blocking antibody (Marom et al. 2017) was used to determine whether CD84 direct targeting can affect MM-induced CD84 and PD-L1 expression on the surface of CD14+cells. Co-culture experiments show that targeting CD84 lowered CD84 (1.6-fold decrease) and PD-L1 expression (1.8-fold decrease) on a CD14+ population co-cultured with MM cells. Moreover, when T cells were included in the co-culture experiments, we observed reduced expression of exhaustion markers PD-1 (1.1-fold decrease) and CTLA4 (1.4-fold decrease) in the presence of the CD84 blocking antibody.Conclusion: We show here that CD84 is expressed on Mo-MDSCs in MM and that the expansion of this myeloid population is strictly associated with MM progression. Disruption of CD84 contacts with a blocking antibody decreases the expression of PD-L1 on CD14+ cells and exhaustion markers on T cells. Thus, our results reveal a novel role for CD84 in regulating PD-L1 in the MM-ME and provides the scientific rationale to investigate whether targeting CD84 expression on Mo-MDSCs can restore T cell functions. To further confirm the role of CD84 regulating T cell activity and Mo-MDSC, in vivo mouse studies are ongoing and results will be presented at the meeting. DisclosuresRosenzweig:Celgene: Speakers Bureau. Krishnan:Sutro: Speakers Bureau; Onyx: Speakers Bureau; Janssen: Consultancy, Speakers Bureau; Celgene: Consultancy, Equity Ownership, Speakers Bureau; Takeda: Speakers Bureau.

Abstract B38: Increasing tumor-infiltrating CD8+ T cell response and checkpoint inhibitor efficacy by enzymatic reduction of tumor hyaluronan in a murine syngeneic pancreatic cancer model

Abstract Inducing an efficient CD8+ T-cell-mediated antitumor immune response at the tumor site is critical for successful immunotherapy. The trafficking and activation of these effector CD8+ T cells to tumors are often inhibited by various immunosuppressive mechanisms in the tumor microenvironment (TME). Hyaluronan (HA), a glycosaminoglycan that accumulates in the TME of many solid tumors, is associated with rapid tumor progression, poor prognosis and increased immunosuppression. We have previously demonstrated in preclinical models that enzymatic degradation of TME HA by intravenous PEGylated recombinant human hyaluronidase PH20 (PEGPH20) enhances anti-Programmed death-ligand 1 (anti-PD-L1) efficacy and increases access of immune cells to the tumor (Clift, AACR 2017 poster #641). In this study, we aimed to extend these findings to a murine syngeneic pancreatic cancer model to explore the pan-tumor potential of combining PEGPH20 and anti-PD-L1 to improve anti-tumor immune response. To test this hypothesis in a pancreatic tumor model, Pan02 murine pancreatic adenocarcinoma cells were engineered to over-express hyaluronan synthase-3 (Pan02/Has3). Peritibial Pan02/Has3 tumors accumulated 10-fold higher levels of HA (1668 ng/mg) compared with Pan02 parental tumors (166 ng/mg) as determined by HA ELISA. HA accumulating Pan02/Has3 tumors were treated with combinations of PEGPH20 and/or anti-PD-L1, and tumor growth was monitored. Treatment with PEGPH20 (1mg/kg, biweekly) resulted in nearly complete removal of HA at 24hrs, the time point at which anti-PD-L1 treatment (5mg/kg, biweekly) was initiated. Tumor burden growth was reduced by 50% with combination of PEGPH20 and anti-PD-L1 versus 21% with PEGPH20 alone (p&amp;lt;0.01) or 5% with anti-PD-L1 alone (p&amp;lt;0.01). To elucidate the underlying mechanism, tumor infiltrating immune cells were analyzed by flow cytometry. We observed a significant increase in the numbers of cytotoxic CD8+ tumor infiltrating lymphocytes (TILs) in tumors treated with PEGPH20 alone compared with the vehicle group. Similarly, tumors treated with PEGPH20 in combination with anti-PD-L1 contained higher numbers of CD8+ TILs, CD4+ TILs, and Natural killer (NK) cells, and had increased CD8:Treg ratios compared to anti-PD-L1 treatment alone. Taken together, our data suggest that tumor HA accumulation may act as a barrier to immune cell access in a mouse model of pancreatic cancer, and that enzymatic reduction of HA can facilitate access of CD8+ T cells and enhance anti-PD-L1 efficacy. These findings are consistent with prior studies and support the ongoing clinical evaluation of combining PEGPH20 with immune checkpoint inhibitors to improve anti-tumor efficacy in HA-accumulating tumors. Citation Format: Benjamin Thompson, Trevor Kimbler, Barbara Blouw, Renee Clift, Yujun Huang, Sanna Rosengren, Curtis B. Thompson, Jisook Lee. Increasing tumor-infiltrating CD8+ T cell response and checkpoint inhibitor efficacy by enzymatic reduction of tumor hyaluronan in a murine syngeneic pancreatic cancer model [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B38.

Expression of PD-L1 on Immune Cells Shows Better Prognosis in Laryngeal, Oropharygeal, and Hypopharyngeal Cancer.

Despite great enthusiasm towards immunotherapy, reliable biomarkers are still lacking. The importance of subsets based on human papillomavirus (HPV) status is supported by a growing body of evidence. However, role of other possible subgroups such as anatomic localization of primary tumor remains controversial. Our objective was to investigate immune cell infiltrate and checkpoint inhibitor proteins in above-mentioned head and neck cancer subsets. Archival tumor samples of 106 laryngeal, oropharyngeal, and hypopharyngeal cancer patients were stained with PD-L1, PD-L2, PD-1, and CTLA-4 antibodies. Proportion of tumor-infiltrating lymphocytes was assessed as well. In HPV-negative tumors, PD-L1 immune cell positivity was associated with better disease-specific survival. PD-L1 expression on immune cells correlated with improved disease-specific survival in laryngeal tumors. Furthermore, PD-L1 immune cell positivity correlated with CTLA-4 expression on immune cells and it was accompanied by high tumor-infiltrating lymphocyte rate. PD-L1 expression on tumor cells and PD-1 status showed strong correlation in all patients and in oropharyngeal and laryngeal localization, but not in hypopharynx. HPV-negative oropharyngeal cancers showed negative PD-L1 status on tumor cells. CTLA-4 positivity was observed in 49.5% and 20.6% on immune cells and on tumor cells, respectively. We concluded that PD-L1 expression on immune cells indicates better prognosis in laryngeal squamous cell carcinoma and in HPV-negative head and neck squamous cell carcinoma. We have not found any essential differences between anatomic subgroups. A possibly distinct role of hypopharyngeal localization regarding immune activity requires further clarification.